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-Origins- Vocab review • • • • Inorganic Organic Abioitc Catalyst LUCA • What are the characteristics of life? • NASA: "A self-sustaining chemical system capable of Darwinian evolution." Four Stages of the Origin of Life • Abiotic synthesis of organic monomers • Formaiton of organic polymers • Protocells: packaging of molecules into a membrane • Living Cells: origin of self-replicating molecules - inheritance Early Earth: Precambrian *Deep Time* accounts for 87% of the geologic timescale Formation of the ocean Oparin-Haldane hypothesis • “Primordial” soup aka organic soup hypothesis – Atmosphere had little O2, but plentiful in H2O vapor, H2 gas, CH4 and NH3 – Reducing environment – Abiotic synthesis of organic compounds via redox reaction (oxidation-reduction reactions) REDOX: transfer of electrons from one molecule to another • An electron donator = oxidized, becomes ____ charged…loss = oxidized • An electron acceptor = reduced, becomes _____ charged…gain=reduced • Important role in biological energy “transactions” • Associated with free radicals • Abnormal redox states can cause sepsis, hypoxia, shock 1953: Miller-Urey experiment Hypothesized…organic compounds that formed… • No free oxygen present – so no oxidation • No bacteria – so no decomposition • Washed into ocean = warm, organic soup from which life could arise Spoiler alert • N2 gas, not NH3 was more abundant… • Repeated experiments with more likely atmospheric recipes have yielded no organic molecules Pocket Hypothesis • Atmosphere near volcanic openings • Reducing environments • Replicated deep ocean thermal vent environment, iron-nickel sulfides reduced N2 to NH3 in a matter of minutes. Iron-Sulfur World hypothesis • Deep sea thermal vents provided all elements and conditions necessary for abiotic synthesis • Iron and Nickel sulfide molecules act as a catalyst • Carbon monoxide, ammonia, and hydrogen sulfide are reduced • http://www.bbc.co.uk/nature/habitats/Hydrot hermal_vent#p00fff1y Extra bonus • Inorganic iron-nickel sulfides have a charged surface – attract amino acids and bind them together… Extraterrestrial Origins Hypothesis • Organic molecules present in some meteorites • Could have seeded chemical origin of life on the planet • A martian meteorite had what appeared to be fossilized bacteria present • Bacteria from another planet arrived here via meteorite and seeded the whole shebang Protein first hypothesis • Polymerization of amino acids in dry heat, form proteinoids • Proteinoids form microspheres • Protein enzymes arose before DNA RNA first hypothesis • Need a way to pass down coded information from one generation to the next • RNA can carry out enzyme like reactions • Ribozymes • Can catalyze its own synthesis proteins associate with it and speed it up • Haven’t seen it happen in “the wild” • Natural selection can act upon it… Spoiler alert • Nucleotides are complicated • Chances that nucleic acids were made spontaneously = immensely unfavorable odds Membrane-first hypothesis • Protocell (protobiont) • Outer membrane • http://exploringorigins.org/fattyacids.html • http://exploringorigins.org/protocells.html • Why is a membrane critical? – Regulation and maintenance of cellular activities Other ideas… • http://www.crystalinks.com/nativeamcreation .html • Various other religious beliefs Not science. What’s the difference? Protobionts • Groups of abiotically produced molecules surrounded by a “membrane” • Simple reproduction and metabolism • Maintenance of internal chemical environment, different from surroundings • Examples: – Liposomes – Coacervates Coacervates Liposomes: Form spontaneously in water Capable of reproduction and simple metabolism • Simple RNA sequences could carry genetic information • RNA could have been a template for DNA Geology • Index fossils and relative dating • Absolute dating and radiometric techniques (K-Ar) • Fossils • Oldest prokaryotic fossils: resemble cyanobacteria Oxygen in the atmosphere • Photosynthetic bacteria (cyanobacteria) • Formed ozone when struck by lightning Endosymbiotic Theory • Size, own DNA and some protein production, binary fission, outer membrane resembles bacterial cell Multicellularity • Cell specialization • Cells in contact and actions are coordinated Many questions remain… • DNA? • Association of RNA with amino acids to build proteins? • Electron transport systems for energy transfer? • Origins of eukaryotic cells? 1969 • Advent of 5 kingdom system DNA and Protein Sequencing • 3 Domain system • replaces kingdom monera
